World 4-5 is the fifth level of World 4. It is a snow level taking place underwater.
The player starts at a pool of water with a Cheep Cheep. A green Warp Pipe takes them underwater where a Roulette Block can be found at first. Cheep Chomps are common in the level where they frequently chase after the player. A Cheep Chomp can first be sighted just after the Roulette Block. This is followed by a blue pipe with a strong current which can push Mario further down the level. Many Cheep Cheeps can also be found, some of which have trails of coins behind them. Another blue pipe with current can be found. Further down lies a Coin Roulette Block with another Cheep Chomp. Shortly after is the checkpoint. A ? Block containing a Fire Flower can be found, followed by a Red Ring and a Cheep Chomp. Continuing on is another Cheep Chomp and the second Star Coin. Going upwards and to the right is the last section with several more Cheep Cheeps and a Cheep Chomp, followed by the exit pipe back to the overworld. There is a small pool of water with Cheep Cheeps, followed by a staircase-like hill and the flagpole.
- Star Coin 1: Above the third blue pipe a yellow pipe can be found on the ceiling. Entering it takes Mario back to land, where a single Cheep Cheep can be found in the water along with four water current-producing pipes with the Star Coin just above them. To obtain it, Mario will need to perform a ground pound into the water just above the Star Coin, while avoiding the Cheep Cheep.
- Star Coin 2: The second Star Coin can be easily seen after the checkpoint. However, it cannot be reached normally as there are hidden blocks enclosing it. Mario will have to swim upwards the next path and instead of continuing right, swim left and navigate downwards to the Star Coin.
- Star Coin 3: At the beginning of the last section, there is a green Warp Pipe on the floor. It takes Mario to another area with the Star Coin, two Cheep Cheeps, water current and a ? Switch. To obtain the Star Coin, Mario needs to activate the ? Switch to turn off the current, then quickly swim to the Star Coin while avoiding the Cheep Cheeps.